1. Field of the invention
The present invention relates to a novel method of treatment of heavy hydrocarbon oil. More particularly, the present invention relates to a method of treatment of heavy hydrocarbon oil in which a naphtha fraction, a kerosene fraction and a gas oil fraction can be obtained efficiently with a high yield by hydrotreatment of the heavy hydrocarbon oil. It also relates to a method of treatment of heavy hydrocarbon oil in which a naphtha fraction, a kerosene fraction and a gas oil fraction can be obtained efficiently with a high yield by hydrotreatment, followed by fluid catalytic cracking, thermal hydrocracking with a slurry bed and further elaborate treatments of the heavy hydrocarbon oil or the vacuum distilled heavy hydrocarbon oil.
2. Description of Related Art
Various methods have been proposed for catalytic hydrotreatment of heavy hydrocarbon oil. For example, a method comprising demetallization and hydrodesulfurization was disclosed in Laid Open Japanese Patent Application Showa 62-89793. Desulfurization is the main object of this method and the method has a problem that the yield of the fraction of 343.degree. C. or lower is low. Another method utilizing a catalyst comprising metals of the group VIA or the group VIII of the Periodic Table supported on a supporter comprising an iron-containing aluminosilicate and inorganic oxides for hydrocracking of heavy hydrocarbon oil was disclosed in Laid Open Japanese Patent Application Heisei 2-289419. A high cracking yield can be obtained by utilizing the disclosed catalyst but this method has a problem that the contents of sulfur compounds and nitrogen compounds in the fraction of 343.degree. C. or higher are high and hence the quality of the product is inferior. A method of hydrotreating heavy hydrocarbon oil by successive demetallization, hydrodesulfurization and hydrocracking was disclosed in Laid Open Japanese Patent Application Heisei 1-275693. The main object of this method is the treatment of heavy distillates containing light cycle oil and main components of the product oil are gas (C.sub.1 .about.C.sub.4) and heavy light naphtha. This method was not intended for the treatment of heavy hydrocarbon oil containing an asphaltene fraction.
In conventional methods of catalytic hydrotreatment of heavy hydrocarbon oil directly, the heavy hydrocarbon oil is first hydrotreated with a fixed bed, a moving bed or a fluidized bed mainly for demetallization and then hydrodesulfurized or hydrotreated with a fixed bed or a fluidized bed. In the operation in which desulfurization is the main part, the reaction temperature is increased to compensate for deactivation of catalysts and this situation causes the problem that the conversion during the whole period of the operation is very low. On the other hand, in the operation in which cracking is the main part, the conversion can be increased to some degree but a problem regarding the quality of the product remains that the content of sulfur in the residue fraction is increased while deactivation of the catalyst proceeds. Moreover, the operation in which cracking is the main part requires complicated control of the processes and the desulfurization and the cracking can not be controlled independently with each other.
Recently, the price of crude oil has become high, the crude oil is becoming heavier and the demand for lighter hydrocarbons are increasing. Thus, development of technology for the cracking of residue oil comprising heavy hydrocarbon oil and for efficient production of the naphtha fraction and the gas oil fraction for transportation fuel has been desired. Flexibility of production in which the constitution of products can be varied according to the season and the location is particularly important for making a satisfactory response to the change of demand.
Various methods have been proposed to solve the problems described above. For example, a method of treating atmospheric reside by the combination of the atmospheric residue hydrodesulfurization process and the residue fluid catalytic cracking (R-FCC) was reposed. This method has a problem that the cracking in the atmospheric residue hydrodesulfurization process is insufficient and a high capacity R-FCC process is required. This method has another problem that a large amount of catalytically cracked gas oil fraction of lower value is produced which has a lower cetane number and is not suitable for direct use as transportation gas oil, such as diesel engine fuel.
In another method proposed, after separation of atmospheric residue to vacuum gas oil and vacuum residue by vacuum distillation, the vacuum gas oil and vacuum gas oil obtained by hydrotreatment of the vacuum residue are combined together and the combined oil is hydrodesulfurized and then treated by the R-FCC process. This method can treat relatively heavier oil but has a problem that the main product of the method is FCC gasoline and oils of lower value like cracked gas oil fraction and cracked residue are produced simultaneously. This method can not produce high quality gas oil fractions other than the FCC gasoline.
In still another method proposed, vacuum residue, such as the one in the preceding method, is desulfurized with a fixed bed and then treated by the R-FCC process. This method has problems that a long operation of the desulfurization with the fixed bed is difficult, that the reactivity in the R-FCC process is possibly decreased remarkably because the feed oil for the process is a product of cracking of vacuum residue and that, in addition to the FCC gasoline, a large amount of lower value oils like cracked gas oil fraction and cracked residue are produced simultaneously.
Other related methods were proposed in Japanese Patent Publications Showa 59-31559, Showa 61-8120, Heisei 1-15559, and Heisei 1-38433 and Laid Open Japanese Patent Application Showa 63-258985. These methods all have difficult problems, such as treatment of asphaltene, complicated processes and the like.
Thus, it has been the actual situation that a satisfactory method of efficiently producing the naphtha fraction and the light oil fraction for transportation fuel by the cracking of residue can not be found and that such a method has been urgently desired.